Apparatus and method for forming polymer crumb

Abstract

The present invention provides a contactor apparatus and method for removing solvent from a polymer cement. The resulting polymer is substantially free of solvent and exhibits improved porosity and more uniform particle size distribution. In one embodiment, a contactor apparatus consists of a cylindrical casing having a high pressure section, a convergence section, a high velocity section, a divergence section, and a discharge section. The polymer cement is introduced into the high pressure section to significantly and unexpectedly improve solvent removal. The convergence and divergence sections preferably have cross-sectional areas that correspond to an effective angle from about 4° to about 65°. The polymer cement is mixed with high pressure steam. After converging, the polymer cement forms more uniform droplets due to high shear of steam. In the divergence and discharge sections, the polymer is substantially devolatized.

What is claimed is:  
     
         1 . A contactor apparatus for separating solvent from a polymer cement comprising: 
 a first section having an inlet for the polymer cement;    a second section having a converging cross-sectional area;    a third section having a smaller cross-sectional area in comparison to the first section;    a fourth section having a diverging cross-sectional area; and    a discharge section having a larger cross-sectional area in comparison to the third section.    
     
     
         2 . The apparatus of  claim 1 , wherein the second section has an effective angle of convergence from about 4° to about 65°, and the fourth section has an effective angle of divergence from about 4° to about 65°.  
     
     
         3 . The apparatus of  claim 2 , wherein the second section has an effective angle of convergence between about 4° and about 45°, and the fourth section has an effective angle of divergence between about 4° and about 63°.  
     
     
         4 . The apparatus of  claim 1 , wherein the ratio of cross-sectional areas of the first section to the third section ranges from about 5 to about 7, and the ratio of cross-sectional areas of the discharge section to the third section ranges from about 15 to about 30.  
     
     
         5 . The apparatus of  claim 4 , wherein the third section has a ratio of length to diameter from about 8 to about 12.  
     
     
         6 . The apparatus of  claim 1 , wherein the second section has a decreasing inner diameter and the fourth section has an increasing inner diameter.  
     
     
         7 . The apparatus of  claim 1 , wherein the second section contains a plug having an increasing outer diameter and the fourth section has an increasing inner diameter.  
     
     
         8 . The apparatus of  claim 1 , wherein the inlet for the polymer cement is a slot.  
     
     
         9 . A method for separating solvent from a polymer cement in a contactor apparatus comprising: 
 introducing high pressure steam and the polymer cement into a first section;    mixing the steam and polymer cement in the first section;    flowing the mixture through a second section having a converging cross-sectional area;    forming droplets comprised of the solvent;    flowing the mixture through a third section having a ratio of length to diameter ranging from about 8 to about 12;    flowing the mixture through a fourth section having a diverging cross-sectional area;    flashing the solvent from the polymer;    flowing the polymer and the solvent through a discharge section; and    separating polymer particles having improved particle size distribution and porosity from the solvent.    
     
     
         10 . The method of  claim 9 , wherein the second section has an effective angle of convergence from about 4° to about 65°, and the fourth section has an effective angle of divergence from about 4° to about 65°.  
     
     
         11 . The method of  claim 10 , wherein the second section has an effective angle of convergence between about 4° and about 45°, and the fourth section has an effective angle of divergence between about 4° and about 63°.  
     
     
         12 . The method of  claim 10  wherein the ratio of cross-sectional areas of the first section to the third section ranges from about 5 to about 7, and the ratio of cross-sectional areas of the discharge section to the third section ranges from about 15 to about 30.  
     
     
         13 . The method of  claim 12 , wherein the polymer cement is introduced through a slot in the first section.  
     
     
         14 . The method of  claim 9 , wherein the second section has a decreasing inner diameter and the fourth section has an increasing inner diameter.  
     
     
         15 . The method of  claim 9 , wherein the second section contains a plug having an increasing outer diameter and the fourth section has an increasing inner diameter.  
     
     
         16 . The method of  claim 9 , wherein the solvent begins to de-volatize in the fourth section.  
     
     
         17 . The method of  claim 9 , wherein the polymer is a conjugated diene polymer or copolymer.  
     
     
         18 . The method of  claim 9 , wherein the polymer particles comprise between about 90% to about 98.5% by weight of the polymer.  
     
     
         19 . The method of  claim 9 , wherein the high pressure steam is about 100 psig to about 350 psig.  
     
     
         20 . The method of  claim 9 , wherein high pressure steam is combined with the polymer cement according to a weight ratio of from 0.4:1 to about 1:1.